Hardware iSCSIHost connects to storage through a HBA capable of offloading the iSCSI and network processing. Hardware adapters can be dependent or independent.

Software iSCSIHost uses a software-based iSCSI initiator in the VMkernel to connect to storage.

Set Up Independent Hardware iSCSI Adapters in the vSphere Storage Guide on page 71.
An independent hardware iSCSI adapter is a specialized third-party adapter capable of accessing iSCSI storage over TCP/IP. This iSCSI adapter handles all iSCSI and network processing and management for your ESXi system.

Network configuration for Independent Hardware iSCSI adapters is done on the HBA. No VMkernel interface is required.

About Dependent Hardware iSCSI Adapters in the vSphere Storage Guide on page 74.
A dependent hardware iSCSI adapter is a third-party adapter that depends on VMware networking, and iSCSI configuration and management interfaces provided by VMware.

About the Software iSCSI Adapter in the vSphere Storage Guide on page 81.
The software-based iSCSI implementation use standard NICs to connect a host to a remote iSCSI target on the IP network.

Dependent and Software iSCSI adapters require a VMkernel to be configured.

Virtual Disk Thin Provisioning in the vSphere Storage Guide on page 253.
Thin provisioned vmdks report allocated size to the guest but only consumes space as data is written to the vmdk.
A thin provisioned vmdk can grow to consume its allocated size.
Thin provisioned vmdks allow for over-provisioning of datastores.
Thin provisioned vmdks save space by only consuming the space need to store data.

Array Thin Provisioning and VMFS Datastores in the vSphere Storage Guide on page 257.
Thin-provisioned LUNs report the LUNs logical size which may be larger than the physical capacity of the disk backing the LUN.
Thin-provisioned LUNs can grow to consume the allocated/logical size.
Array thin provisioning allows for over-provisioning on the array.
VAAI allows the host to be aware of the underlying thin-provisioned LUN and the space usage.
VAAI allows for monitoring of the physical space to provide warning and alerts for over-commitment thresholds and out-of-space conditions.
VAAI also informs the array about datastore space which has been freed when files are deleted or removed to allow the array to reclaim the freed blocks.

Zoning defines which HBAs/ports can connect to which targets. Zoning controls and isolates paths in the storage fabric.

Use a single-initiator zoning or a single-initiator-single-target zoning.
Single-initiator-single target the preferred zoning practice for ESXi.

LUN masking is a process that makes a LUN available to some hosts and unavailable to other hosts.

The MASK_PATH module can be used to mask devices from a host. This can be used to prevent a host from accessing storage devices or LUNs or from using individual paths to a LUN. This is done using esxcli to create a claimrule which masks the path or device. See Mask Paths in the vSphere Storage Guide on page 192.

iSCSI ports of the array target must reside in the same broadcast domain and IP subnet as the VMkernel adapters.

All VMkernel adapters used for iSCSI port binding must reside in the same broadcast domain and IP subnet.

All VMkernel adapters used for iSCSI connectivity must reside in the same virtual switch.

Port binding does not support network routing.

Do not use port binding when:

Array target iSCSI ports are in a different broadcast domain and IP subnet.

VMkernel adapters used for iSCSI connectivity exist in different broadcast domains, IP subnets, or use different virtual switches.

Routing is required to reach the iSCSI array.

When binding a portgroup/VMkernel adapter to an iSCSI adapter only the VMkernel adapters which are compatible with iSCSI port binding requirements and available physical adapters are listed.
Compliant VMkernel adapters are configured with only a single active uplink and no standby uplinks.

– Determine use case for and configure array thin provisioning
Array Thin Provisioning and Virtual Disk Thin provision allows allocation of more space than is physically available.
The use case is to provide more efficient use of capacity by consuming only the amount of space needed to store data.
This can be done on the datastore using thin provisioned virtual disk or on the array using thin provisioned LUNs.

vHersey

Hersey Cartwright is an IT professional with extensive experience designing, implementing, managing, and supporting technologies that improve business processes. Hersey is Solutions Architect for HPE SimpliVity covering Virginia, Washington DC, and Maryland. He holds the VMware Certified Design Expert (VCDX-DV #128) certification. Hersey actively participates in the VMware community and was awarded the VMware vExpert title in 2016, 2015, 2014, 2013, and 2012. He enjoys working with, teaching, and writing about virtualization and other data center technologies. Follow Hersey on Twitter @herseyc